Spring 2005
MWF 11:30
Instructor: Dr. Bruce Law, CW
327, Tel: 532-1618.
REVIEW QUESTIONS OF Home Work 3
R3. The vertical component is being
acceleration by gravity while the horizontal component has zero acceleration
(i.e. it`s velocity is constant).
R4. False. The
horizontal component remains constant however the vertical component changes
with time.
R5. The horizontal component remains
constant when the rock is rising as well as falling.
R6. The vertical component decreases as the
rock rises and increases as the rock falls.
R10. The projectile has an initial velocity
of 100m/s, up. The acceleration due to gravity (which is 10m/s2,
down) decreases the velocity as the projectile rises – this is because
the velocity and acceleration are pointing in opposite directions. On the way
down both the velocity and acceleration are pointing in the same direction
(i.e. down) therefore the velocity will increase with time. By symmetry the
projectile must hit the ground with a velocity of 100m/s, down.
EXCERISES OF Home Work 3
E1. The crate will not hit the Camaro, but will crash a distance beyond it determined by
the height and speed of the plane.
E9. Gravity acts on the bullet and would
make it hit below the target. To compensate for this effect the rifle must be
aimed slightly upwards.
PROBLEMS OF Home Work 3
P1. It`s
horizontal speed is 10m/s (because this remains constant). It`s
vertical speed (which was initially 0m/s because the ball was thrown
horizontally) can be calculated from
v = gt = 10m/s2
x 1s = 10m/s
P2. (a) For height from the ground d=0.5gtt=0.5*10*30*30=4500m. (b)
Distance engine travels horizontally, x=vt=280*30=8400m. (c) The engine would be immediate below the
airplane because both the airplane and engine has the same (constant)
horizontal speed.